.clearfix::after {
    content: '';
    display: block;
    clear: both;
}
.header{
    width: 100%;
    background:crimson;
    color:#fff;
    height: 40px;
    line-height: 40px;
    position: fixed;
    left:0 ;
    top:0;
}
.header .topnav>li {
    float:left;
    padding:0 10px;
    text-align: center;
    width: 20%;
    height: 40px;
    box-sizing: border-box;
    position: relative;

}
.header .topnav>li:hover{
    background:#fff;
    border:2px solid #ccc;
    border-bottom: none ;
    line-height: 36px;
    

}
.header .topnav>li a{
    color:#fff;
}
.header .topnav>li:hover a{
    color:black;
}

.header .topnav>li .submenu{
    text-align: left;
    line-height: 1.5;
    width: 400px;
    display: none;
    border: 2px solid #ccc;
    box-sizing: border-box;
    position: absolute;
    right: -2px;
    background: #fff;
    color: black;
    

}
.header .topnav>li:hover .submenu{
    display: block
}

.header .topnav>li:hover::after{
    content:"";
    position: absolute;
    width: 100%;
    height: 5px;
    background: #fff;
    bottom: 0;
    left:0;
}

.container .content{
    margin-top: 40px;
    padding: 20px;
}